Different hardware description languages (such as Very High Speed Integrated Circuit Hardware Description Language (VHDL)) are used in electronic design automation to described different types of circuit designs (including digital, mixed-signal, etc.). These hardware description languages are used to describe a logic circuit according to structure, data flow behavior, function, etc.
Some hardware designs include timing critical structures (e.g., adders, multiplexer, etc.). Tools for synthesis, placement, and wiring generally do not provide a sufficient physical implementation or representation for these timing critical structures. In particular, these timing critical structures need special placement and wiring or have a very ordered structure that needs special guidance for synthesis.